When package.json contains packages from non-npmjs registries (JSR, AWS
CodeArtifact, private registries, local workspace packages), the registry
fetch inside Promise.all would reject and hard-fail the entire update
command with a 404 or network error.

Wrap each per-package getNpmPackageJson call in a .catch() so that fetch
failures emit a warning and return a partial sentinel object. The existing
reduce step already handles partial objects correctly: auto-discovered
packages are silently skipped while explicitly-requested packages still
produce a clear SchematicsException, preserving intentional error
visibility.

Closes angular#28834